1. Field of the Invention
The present invention relates to a light source (including a planar light source) comprising electron emitters each having an upper electrode and a lower electrode that are disposed in an emitter.
2. Description of the Related Art
Recently, electron emitters having a drive electrode and a common electrode have been finding use in various applications such as field emission displays (FEDs) and backlight units. In an FED, a plurality of electron emitters are arranged in a two-dimensional array, and a plurality of phosphors are positioned in association with the respective electron emitters with a predetermined gap left therebetween.
Conventional electron emitters are disclosed in Japanese Laid-Open Patent Publication No. 1-311533, Japanese Laid-Open Patent Publication No. 7-147131, Japanese Laid-Open Patent Publication No. 2000-285801, Japanese Patent Publication No. 46-20944, and Japanese Patent Publication No. 44-26125, for example. All of these disclosed electron emitters are disadvantageous in that since no dielectric body is employed in the emitter, a forming process or a micromachining process is required between facing electrodes, a high voltage needs to be applied to emit electrons, and a panel fabrication process is complex and entails a high panel fabrication cost.
It has been considered to make an emitter of a dielectric material. However, various theories about the emission of electrons from a dielectric material have been presented in the documents: Yasuoka and Ishii, “Pulse electron source using a ferrodielectric cathode”, J. Appl. Phys., Vol. 68, No. 5, p. 546-550 (1999), and V. F. Puchkarev, G. A. Mesyats, On the mechanism of emission from the ferroelectric ceramic cathode, J. Appl. Phys., Vol. 78, No. 9, 1 Nov. 1995, p. 5633-5637.
In the conventional electron emitters described above, electrons that are restrained on the surface of a dielectric body, the interface between the dielectric body and an upper electrode, and the defective level in the dielectric body are discharged by an inversion of the polarization of the dielectric body. That is, if the polarization of the dielectric body is inverted, then the amount of emitted electrons is substantially constant, not dependent on the voltage level of an applied voltage pulse.
However, the conventional electron emitters are problematic in that the electron emission is not stable and can be performed at most several tens of thousands times, and the electron emitters are not practical when used as light sources, for example.